JP7272440B2 - Acoustic Wave Filters and Multiplexers - Google Patents

Description

The present invention relates to an elastic wave filter and a multiplexer provided with the elastic wave filter.

In Patent Document 1, in a longitudinally coupled resonator in which a plurality of IDT (InterDigital Transducer) electrodes and reflectors are arranged in the acoustic wave propagation direction, the main excitation region of the IDT electrode or between the main excitation region and the reflector An elastic wave filter is disclosed in which a sub-excitation region in which the electrode finger pitch changes stepwise is arranged between them. According to this, it is said that the low-loss property of the acoustic wave filter is improved.

WO2003/003574

However, as in Patent Document 1, in an elastic wave filter including a longitudinally coupled resonator in which a sub-excitation region in which the distribution of electrode finger pitches changes regularly, unnecessary acoustic waves are excited and sufficiently damped. There is a problem that characteristics cannot be obtained. Moreover, there is a problem that the isolation characteristic of the multiplexer including the elastic wave filter is degraded.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an elastic wave filter with improved attenuation characteristics and a multiplexer with improved isolation characteristics.

To achieve the above object, an elastic wave filter according to an aspect of the present invention includes a piezoelectric substrate, a plurality of IDT electrodes provided on the substrate and arranged in parallel in an elastic wave propagation direction, and the plurality of and a reflector arranged adjacent to the IDT electrode in the acoustic wave propagation direction, wherein each of the plurality of IDT electrodes and the reflector is , a plurality of electrode fingers extending in a direction intersecting the elastic wave propagation direction and arranged parallel to each other; The distance between the electrode finger and the (k+1)-th electrode finger is defined as the k-th electrode finger pitch, and (2) the (k-1)-th electrode finger, the k-th electrode finger, and the (k+1)-th electrode Difference between the k-th electrode finger pitch and the interval average electrode finger pitch which is the average of the (k−1)th electrode finger pitch and the (k+1)th electrode finger pitch among three adjacent electrode fingers called fingers is divided by the overall average electrode finger pitch, which is the average pitch of the entire electrode fingers of the IDT electrode or reflector including the three adjacent electrode fingers, is defined as the pitch deviation rate of the k-th electrode finger. and (3) the pitch deviation rate obtained by calculating the pitch deviation rate of the k-th electrode finger for all the electrode fingers of the IDT electrode or reflector including the three adjacent electrode fingers. is defined as the histogram of the pitch deviation rate, at least one of the plurality of IDT electrodes and the reflector has a standard deviation of the pitch deviation rate in the histogram of 1.4% or more.

According to the present invention, it is possible to provide an acoustic wave filter with improved attenuation characteristics and a multiplexer with improved isolation characteristics.

FIG. 1 is a circuit configuration diagram of an elastic wave filter according to an embodiment. FIG. 2 is a schematic plan view showing the electrode configuration of the longitudinally coupled resonator according to the embodiment. FIG. 3 is a graph showing the distribution of electrode finger pitches of the longitudinally coupled resonator according to the embodiment. FIG. 4 is a graph showing the distribution of electrode finger pitches of a longitudinally coupled resonator according to a comparative example. FIG. 5 is a diagram for explaining the action of the irregular electrode finger pitch distribution of the longitudinally coupled resonator according to the embodiment. FIG. 6 is a diagram for explaining the pitch deviation rate and its standard deviation in the irregular electrode finger pitch distribution of the longitudinally coupled resonator according to the embodiment. FIG. 7 is a configuration diagram of a multiplexer and its peripheral circuits according to the first embodiment. 8 is a graph comparing pass characteristics and isolation characteristics of multiplexers according to Example 1 and Comparative Example 1. FIG. FIG. 9 is a graph comparing the voltage standing wave ratios of the multiplexers according to Example 1 and Comparative Example 1; FIG. 10 is a graph showing the relationship between the standard deviation of the pitch deviation rate of the longitudinally coupled resonators and the isolation of the multiplexer. 11A is a circuit configuration diagram of an elastic wave filter according to a second embodiment; FIG. 11B is a graph comparing the pass characteristics of the acoustic wave filters according to Example 2 and Comparative Example 2. FIG. 12A is a graph showing the distribution of the electrode finger arrangement configuration and the electrode finger pitch of the longitudinally coupled resonator of the acoustic wave filter according to Example 3. FIG. 12B is a graph comparing pass characteristics and isolation characteristics of multiplexers according to Example 3 and Comparative Example 3. FIG. FIG. 13 is a configuration diagram of a multiplexer and its peripheral circuits according to the fourth embodiment. 14 is a graph comparing pass characteristics of elastic wave filters according to Example 4, Comparative Example 4, and Comparative Example 5. FIG.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail using embodiment and drawing. It should be noted that the embodiments described below are all comprehensive or specific examples. Numerical values, shapes, materials, constituent elements, arrangement of constituent elements, connection forms, and the like shown in the following embodiments are examples, and are not intended to limit the present invention. Among the constituent elements in the following embodiments, constituent elements not described in independent claims will be described as optional constituent elements. Also, the sizes or size ratios of components shown in the drawings are not necessarily exact.

(Embodiment)
[1. Configuration of elastic wave filter 40 according to embodiment]
FIG. 1 is a circuit configuration diagram of an elastic wave filter 40 according to an embodiment. Also, FIG. 2 is a schematic plan view showing the electrode configuration of the longitudinally coupled resonator 1 according to the embodiment. FIG. 2 shows the planar layout configuration of the IDT electrodes and reflectors constituting the longitudinally coupled resonator 1 and the electrical connection state between the IDT electrodes. Note that the longitudinally coupled resonator 1 shown in FIG. 2 is for explaining a typical planar layout configuration of the IDT electrodes. etc. is not limited to this.

As shown in FIG. 1 , elastic wave filter 40 includes longitudinally coupled resonator 1 , series arm resonators 31 s and 32 s, parallel arm resonators 31 p and 32 p, and input/output terminals 110 and 120 .

Series arm resonators 31 s and 32 s are acoustic wave resonators arranged in series on a path connecting input/output terminal 110 and input/output terminal 120 . Parallel arm resonators 31p and 32p are elastic wave resonators connected between nodes on the path and the ground, respectively.

As shown in FIG. 2, the longitudinally coupled resonator 1 is composed of longitudinally coupled resonators 10 and 20 connected in parallel and arranged between a terminal 130 and an input/output terminal 120 . The longitudinal coupling resonator 10 includes five IDT (InterDigital Transducer) electrodes 11, 12, 13, 14 and 15 arranged side by side in the acoustic wave propagation direction on a substrate having piezoelectricity, and for the five IDT electrodes and reflectors 19A and 19B arranged adjacent to each other in the elastic wave propagation direction. The longitudinal coupling resonance section 20 includes five IDT electrodes 21, 22, 23, 24 and 25 arranged side by side in the elastic wave propagation direction on a substrate having piezoelectricity, and elastic wave propagation for the five IDT electrodes. and reflectors 29A and 29B arranged so as to be directionally adjacent.

The IDT electrodes 11 to 15, 21 to 25 and the reflectors 19A, 19B, 29A and 29B are formed on a piezoelectric substrate. , constitute a surface acoustic wave resonator.

Each of the IDT electrodes 11 to 15, 21 to 25 and the reflectors 19A, 19B, 29A and 29B extends in a direction intersecting the elastic wave propagation direction and is composed of a plurality of electrode fingers arranged parallel to each other. there is

The IDT electrode 11 is composed of comb electrodes 11a and 11b. The comb-shaped electrode 11a is an example of a first comb-shaped electrode, and includes some electrode fingers among the plurality of electrode fingers forming the IDT electrode 11 and a bus bar electrode connecting one ends of the some electrode fingers. and is connected to the input/output terminal 120 . The comb-shaped electrode 11b is an example of a second comb-shaped electrode, and is an electrode finger of the other portion among the plurality of electrode fingers forming the IDT electrode 11 and a bus bar electrode connecting the other ends of the electrode fingers of the other portion. connected to ground. The electrode fingers forming the comb-shaped electrode 11a and the electrode fingers forming the comb-shaped electrode 11b are inserted into each other. The IDT electrode 13 is composed of comb electrodes 13a (first comb electrodes) and 13b (second comb electrodes). The comb electrode 13a is connected to the input/output terminal 120, and the comb electrode 13b is grounded. The IDT electrode 15 is composed of comb electrodes 15a (first comb electrodes) and 15b (second comb electrodes). The comb electrode 15a is connected to the input/output terminal 120, and the comb electrode 15b is grounded. The IDT electrode 21 is composed of a comb-shaped electrode 21a (first comb-shaped electrode) and 21b (second comb-shaped electrode). The comb-shaped electrode 21a is connected to the input/output terminal 120, and the comb-shaped electrode 21b is grounded. The IDT electrode 23 is composed of a comb-shaped electrode 23a (first comb-shaped electrode) and 23b (second comb-shaped electrode). The comb electrode 23a is connected to the input/output terminal 120, and the comb electrode 23b is grounded. The IDT electrode 25 is composed of a comb-shaped electrode 25a (first comb-shaped electrode) and 25b (second comb-shaped electrode). The comb electrode 25a is connected to the input/output terminal 120, and the comb electrode 25b is grounded.

The IDT electrode 12 is composed of comb electrodes 12a and 12b. The comb-shaped electrode 12b is an example of a first comb-shaped electrode, and includes some electrode fingers among the plurality of electrode fingers forming the IDT electrode 12 and a bus bar electrode connecting one ends of the some electrode fingers. and is connected to the terminal 130 . The comb-shaped electrode 12a is an example of a second comb-shaped electrode, and includes the other electrode fingers of the plurality of electrode fingers forming the IDT electrode 12 and the bus bar electrodes that connect the other ends of the other electrode fingers. connected to ground. The electrode fingers forming the comb-shaped electrode 12a and the electrode fingers forming the comb-shaped electrode 12b are interdigitated with each other. The IDT electrode 14 is composed of a comb-shaped electrode 14b (first comb-shaped electrode) and 14a (second comb-shaped electrode). The comb-shaped electrode 14b is connected to the terminal 130, and the comb-shaped electrode 14a is grounded. The IDT electrode 22 is composed of a comb-shaped electrode 22b (first comb-shaped electrode) and 22a (second comb-shaped electrode). The comb-shaped electrode 22b is connected to the terminal 130, and the comb-shaped electrode 22a is grounded. The IDT electrode 24 is composed of a comb-shaped electrode 24b (first comb-shaped electrode) and 24a (second comb-shaped electrode). The comb electrode 24b is connected to the terminal 130, and the comb electrode 24a is grounded.

The number of IDT electrodes forming the longitudinally coupled resonance section 10 should be two or more, and the number of IDT electrodes forming the longitudinally coupled resonance section 20 should be two or more. Moreover, the number of reflectors constituting the longitudinally coupled resonator 10 may be one or more, and the number of reflectors constituting the longitudinally coupled resonator 20 may be one or more.

Further, in acoustic wave filter 40 according to the present embodiment, the number of longitudinally coupled resonators constituting longitudinally coupled resonator 1 is arbitrary, and longitudinally coupled resonator 1 may be any one of longitudinally coupled resonators 10 and 20. It may consist of only

In acoustic wave filter 40 according to the present embodiment, the number of series arm resonators and the number of parallel arm resonators are arbitrary, and there are no series arm resonators 31s and 32s and parallel arm resonators 31p and 32p. may

Further, in the elastic wave filter 40 according to the present embodiment, another circuit element and wiring are inserted between the paths connecting the elastic wave resonators, the input/output terminals, and the ground disclosed in FIG. good too.

[2. Electrode finger pitch and pitch deviation rate]
As shown in FIG. 2, each of the IDT electrodes 11 to 15, 21 to 25, and the reflectors 19A, 19B, 29A and 29B extends in a direction intersecting the elastic wave propagation direction and is arranged in parallel with each other. It is composed of electrode fingers Fe.

The elastic wave filter 40 according to the present embodiment is characterized by the distribution of the electrode finger pitch P, which is the distance between the adjacent electrode fingers Fe (the distance between the center lines of the electrode fingers Fe in the elastic wave propagation direction). there is Here, as shown in FIG. 2, in one IDT electrode or one reflector (for example, the IDT electrode 11), the first electrode finger Fe (1) and the second electrode finger Fe (2 ) (the distance between the center line of the electrode finger Fe(1) in the elastic wave propagation direction and the center line of the electrode finger Fe(2) in the elastic wave propagation direction) is defined as the electrode finger pitch P Define as (1). Thereafter, similarly, the electrode finger pitch P(2) of the electrode finger Fe(2), the electrode finger pitch P(3) of the electrode finger Fe(3), and the electrode finger pitch P(4) of the electrode finger Fe(4) is defined. That is, the distance between the electrode finger Fe(k) and the electrode finger Fe(k+1) (the distance between the center line of the electrode finger Fe(k) in the elastic wave propagation direction and the center line of the electrode finger Fe(k+1) in the elastic wave propagation direction) distance) is defined as the electrode finger pitch P(k) (k is a natural number) of the k-th electrode finger Fe(k) in the elastic wave propagation direction.

FIG. 3 is a graph showing the distribution of the electrode finger pitch P(k) of the longitudinally coupled resonator 1 according to the embodiment. The figure shows the electrode finger pitch P(k) of the longitudinally coupled resonator 10 constituting the longitudinally coupled resonator 1 . The horizontal axis indicates the positions of the electrode fingers Fe(1) to Fe(200) constituting the longitudinal coupling resonance section 10, and the vertical axis indicates the electrode finger pitch P of the electrode fingers Fe(k). (k) is shown.

As shown in FIG. 3, in the longitudinally coupled resonator 10 according to the present embodiment, the electrode finger pitch P(k) has electrode finger sections arranged irregularly.

FIG. 4 is a graph showing the distribution of the electrode finger pitch P(k) of the longitudinally coupled resonator of the acoustic wave filter according to the comparative example. The elastic wave filter according to the comparative example is the same as the elastic wave filter 40 according to the embodiment in that it has an elastic wave resonator in which two elastic wave resonators are connected in parallel. The distribution of the electrode finger pitch P(k) of the acoustic wave resonator is different. FIG. 4 shows the electrode finger pitch P(k) of the longitudinally coupled resonator according to the comparative example.

As shown in FIG. 4, in the longitudinally coupled resonator according to the comparative example, the electrode finger pitches P(k) are regularly arranged. Specifically, in the longitudinally coupled resonator according to the comparative example, a section having a constant electrode finger pitch P between three or more adjacent electrode fingers Fe is provided in the same IDT electrode or reflector. As an example in which the electrode finger pitches P(k) are regularly arranged, in addition to the example shown in FIG. (the electrode finger pitch P(k) has a constant slope: a so-called gradation pitch).

On the other hand, in the longitudinally coupled resonance section 10 according to the present embodiment, the constant electrode finger pitch P is not provided between three or more adjacent electrode fingers Fe, and three or more adjacent electrode fingers Fe has an IDT electrode or reflector whose electrode finger pitch P(k) does not have a constant inclination.

In the longitudinally coupled resonator 10 according to the present embodiment shown in FIG. 3, the electrode finger pitches P(k) are arranged irregularly in all of the IDT electrodes 11 to 15 and the reflectors 19A and 19B. However, the longitudinally coupled resonator of the elastic wave filter according to the present invention is not limited to this. That is, in the elastic wave filter according to the present invention, the electrode finger pitch P(k) is irregular between three or more adjacent electrode fingers Fe in at least one of the IDT electrodes 11 to 15 and the reflectors 19A and 19B. It suffices if the electrode finger sections are arranged in a row.

It should be noted that the electrode finger pitch P(k) of the longitudinally coupled resonator 20 constituting the longitudinally coupled resonator 1 also has an irregular distribution, similar to the electrode finger pitch P(k) of the longitudinally coupled resonator 10. may be Moreover, the distributions of the electrode finger pitches P(k) of the longitudinal coupling resonance section 10 and the longitudinal coupling resonance section 20 may be the same or different.

FIG. 5 is a diagram for explaining the action of the irregular electrode finger pitch P(k) distribution of the longitudinally coupled resonator 1 according to the embodiment. The figure shows a schematic cross-sectional view of a substrate 60 having piezoelectric properties and electrode fingers Fe(k) to Fe(k+4) formed on the substrate 60 . The electrode fingers Fe(k) to Fe(k+4) shown in FIG. 5 have irregular electrode finger pitches P(k) to P(k+4).

First, it is assumed that electrode fingers Fe(k) to Fe(k+4) shown in FIG. 5 are electrode fingers arranged in the same IDT electrode (operation 1). Here, the electrode finger Fe(k), the electrode finger Fe(k+2), and the electrode finger Fe(k+4) constitute a first comb electrode to which the signal potential (HOT) is applied. Further, the electrode finger Fe(k+1) and the electrode finger Fe(k+3) constitute a second comb-shaped electrode connected to the ground (GND). Here, the electrode finger pitches P(k), P(k+1), P(k+2), and P(k+3) have an irregular electrode finger pitch distribution.

At this time, the phase of the wavelength (the wavelength of the acoustic wave of HOT2) of the acoustic wave (the solid line in FIG. 5) excited by the electrode finger Fe(k+2), which is the HOT electrode, and the electrode finger Fe(k), which is the HOT electrode, A phase shift occurs with the acoustic wave to be excited (the dashed-dotted line in FIG. 5). Further, the phase of the wavelength (the wavelength of the acoustic wave of HOT2) of the acoustic wave (the solid line in FIG. 5) excited by the electrode finger Fe(k+2), which is the HOT electrode, and the phase of the acoustic wave excited by the electrode finger Fe(k+4), which is the HOT electrode, A phase shift occurs between the phase of the received acoustic wave (broken line in FIG. 5). For this reason, mismatching in acoustic impedance is likely to occur among the electrode finger Fe(k), the electrode finger Fe(k+2), and the electrode finger Fe(k+4), which are HOT electrodes.

Next, electrode fingers Fe(k) to Fe(k+3) shown in FIG. Assume that it belongs to the IDT electrode on the output side (operation 2). Here, the electrode finger Fe(k), the electrode finger Fe(k+2), and the electrode finger Fe(k+4) constitute a first comb electrode to which the signal potential (HOT) is applied. Further, the electrode finger Fe(k+1) and the electrode finger Fe(k+3) constitute a second comb-shaped electrode connected to the ground (GND). Here, the electrode finger pitches P(k), P(k+1), P(k+2), and P(k+3) have an irregular electrode finger pitch distribution.

At this time, the acoustic wave excited by the electrode finger Fe(k) on the input-side IDT electrode and the acoustic wave excited by the electrode finger Fe(k+2) are combined with the electrode finger Fe(k+4) on the output-side IDT electrode. When picking up, the phase of the acoustic wave of the electrode finger Fe(k) is out of phase with the phase of the acoustic wave of the electrode finger Fe(k+2), so the electrode finger Fe(k+4) cannot efficiently pick up.

As a method for improving the attenuation characteristic of the longitudinally coupled resonator, the excitation of the signal of the frequency of the attenuation band is suppressed in the electrode finger which is the HOT electrode, and the signal of the frequency of the attenuation band is transferred from the input side IDT electrode to the output side IDT. For example, it should be prevented from propagating to the electrode.

In the case of a conventional longitudinally coupled resonator having a configuration in which the electrode finger pitch P(k) increases or decreases at a constant rate (gradation pitch) with respect to the transition of the electrode finger Fe, a signal with a frequency in the attenuation band is input. Although it is possible to cancel the phase difference so as not to propagate from the side IDT electrode to the output side IDT electrode, the ability to suppress the excitation itself of the signal of the frequency of the attenuation band in the electrode finger which is the HOT electrode is low, and sufficient Attenuation improvement effect is not obtained.

On the other hand, in the elastic wave filter 40 according to the present embodiment, an irregular electrode finger pitch as shown in FIG. By applying the distribution of P, it is possible to suppress the excitation of unnecessary acoustic waves by the above action 1, and to suppress the pickup of the excited acoustic waves by the above action 2. This makes it possible to improve the attenuation characteristics of the elastic wave filter 40 .

Next, the pitch deviation rate D and its standard deviation SD specified in the elastic wave filter 40 according to the present embodiment will be described.

FIG. 6 is a diagram for explaining the pitch deviation rate D and its standard deviation SD in the irregular electrode finger pitch distribution of the longitudinally coupled resonator 1 according to the embodiment.

FIG. 6(a) shows an example of the distribution of the electrode finger pitch P(k) of the IDT electrodes or reflectors forming the longitudinally coupled resonator. The horizontal axis indicates the positions of the electrode fingers Fe(k) constituting the IDT electrodes or reflectors, and the vertical axis indicates the electrode finger pitch P(k) of the electrode fingers Fe(k). .

As described above, (1) the distance (electrode finger Fe (k) is defined as the k-th electrode finger pitch P(k).

Next, (2) in three adjacent electrode fingers, electrode finger Fe(k−1), electrode finger Fe(k), and electrode finger Fe(k+1), the electrode finger pitch P(k−1) and the electrode The average of the finger pitch P(k+1) is defined as the section average electrode finger pitch PM(k) [={P(k−1)+P(k+1)}/2]. At this time, the difference [=P(k)-PM(k)] between the electrode finger pitch P(k) and the section average electrode finger pitch PM(k) is calculated as electrode finger Fe(k-1), Fe(k ) and Fe(k+1), and the value obtained by dividing the average pitch of the entire electrode fingers of the IDT electrode or reflector containing Fe(k+1) by the overall average electrode finger pitch PT, the pitch deviation rate D(k ) [={P(k)−PM(k)}/PT].

Next, (3) the pitch deviation rate D(k) of the electrode fingers Fe(k) is calculated as follows: Calculation is performed for all electrode fingers Fe, and a histogram of the pitch deviation rate D(k) in the IDT electrode or reflector is calculated.

FIG. 6(b) shows an example of the distribution of the pitch deviation rate D(k) of the IDT electrodes or reflectors forming the longitudinally coupled resonator. The horizontal axis indicates the positions of the electrode fingers Fe(k) constituting the IDT electrodes or reflectors, and the vertical axis indicates the pitch deviation rate D(k).

FIG. 6(c) shows an example of a histogram of the pitch deviation rate D(k) of the IDT electrodes or reflectors forming the longitudinally coupled resonator.

Finally, from the histogram of the pitch deviation rates D(k), the standard deviation SD of the pitch deviation rates D(k) of the IDT electrodes or reflectors forming the longitudinally coupled resonator is calculated.

According to the above definition, the stronger the regularity of the electrode finger pitch P(k), the smaller the standard deviation SD of the pitch deviation rate D(k), and the stronger the irregularity of the electrode finger pitch P(k), the pitch deviation rate The standard deviation SD of D(k) increases.

In longitudinally coupled resonator 1 included in elastic wave filter 40 according to the present embodiment, each of IDT electrodes 11 to 15 and reflectors 19A and 19B constituting longitudinally coupled resonator 10 has a pitch deviation rate D(k) of The standard deviation is 1.4% or more. In each of the IDT electrodes 21 to 25 and the reflectors 29A and 29B that constitute the longitudinally coupled resonance section 20, the standard deviation of the pitch deviation rate D(k) in the histogram is 1.4% or more.

Thereby, when an acoustic wave corresponding to the frequency of the attenuation band of the elastic wave filter propagates on the substrate, for example, the phase of the acoustic wave excited by the electrode finger Fe(k) and the phase of the acoustic wave excited by the electrode finger Fe(k+2) Acoustic waves are likely to be out of phase, and acoustic impedance mismatching is likely to occur. Therefore, it is possible to suppress excitation of acoustic waves corresponding to frequencies in the attenuation band of the elastic wave filter. Further, when the acoustic wave excited by the electrode finger Fe(k) and the acoustic wave excited by the electrode finger Fe(k+2) on the input-side IDT electrode are picked up by the output-side IDT electrode, both acoustic waves are out of phase, they cannot be picked up efficiently. Therefore, it becomes possible to improve the attenuation characteristic of the acoustic wave filter 40 .

Note that in the longitudinally coupled resonator according to the comparative example shown in FIG. 4, the regularity of the electrode finger pitch P(k) is strong in each of the IDT electrodes and reflectors, so the standard deviation SD in the above histogram is 1.5. less than 4%. In addition, the electrode finger pitch P(k) increases or decreases at a constant rate with respect to the transition of the electrode finger Fe (the electrode finger pitch P(k) has a constant inclination: a so-called gradation pitch). Since the regularity of the electrode finger pitch P(k) is strong in each of the IDT electrodes and reflectors having the configurations, the standard deviation SD in the above histogram is less than 1.4%.

In longitudinally coupled resonator 1 according to the present embodiment, IDT electrodes 11 to 15 and reflectors 19A and 19B forming longitudinally coupled resonant section 10, and IDT electrodes 21 to 25 forming longitudinally coupled resonant section 20 , at least one of the reflectors 29A and 29B should have a standard deviation SD of 1.4% or more in the above histogram.

As a result, the attenuation characteristics of the elastic wave filter 40 can be effectively improved by setting the standard deviation SD in the histogram to 1.4% or more for the IDT electrodes or reflectors that greatly affect the attenuation characteristics. It becomes possible.

Further, in the longitudinally coupled resonator 1 according to the present embodiment, at least one of the IDT electrodes 11 to 15 forming the longitudinally coupled resonant section 10 and the IDT electrodes 21 to 25 forming the longitudinally coupled resonant section 20 is , a standard deviation SD in the histogram of 1.4% or more, and each of the reflectors 19A, 19B, 29A and 29B may have a standard deviation SD in the histogram of less than 1.4%.

As a result, by applying the irregular electrode finger pitch P(k) to the IDT electrodes that have a large influence on the attenuation characteristics, the attenuation characteristics of the acoustic wave filter 40 can be improved, and the electrode finger pitch P Since the manufacturing variation of (k) can be suppressed, it is possible to stabilize the attenuation pole outside the passband defined by the resonant operation of the reflector.

Further, in the longitudinally coupled resonator 1 according to the present embodiment, one of the IDT electrodes 11 to 15 and 21 to 25 has a standard deviation SD of 1.4% or more in the histogram, And the IDT electrodes 11-15 and other IDT electrodes among 21-25 may have a standard deviation SD of less than 1.4% in the histogram.

As a result, it is possible to improve the attenuation characteristic of the elastic wave filter 40 for one IDT electrode which greatly affects the attenuation characteristic, and to suppress manufacturing variations in the other IDT electrodes, thereby suppressing characteristic deterioration.

Further, in the longitudinally coupled resonator 1 according to the present embodiment, at least one of the reflectors 19A and 19B forming the longitudinally coupled resonator 10 and the reflectors 29A and 29B forming the longitudinally coupled resonator 20 has the histogram , and each of the IDT electrodes 11-15 and 21-25 may have a standard deviation SD of less than 1.4% in the histogram.

As a result, by applying the irregular electrode finger pitch P(k) to the reflectors that greatly affect the attenuation characteristics, the attenuation characteristics of the elastic wave filter 40 can be improved, and the electrode finger pitch P Since the manufacturing variation of (k) can be suppressed, it is possible to stabilize the insertion loss in the passband.

[3. Configuration and characteristics of multiplexer 100 according to embodiment 1]
FIG. 7 is a configuration diagram of the multiplexer 100 and its peripheral circuits according to the first embodiment. As shown in the figure, the multiplexer 100 includes an acoustic wave filter 40, a filter 50, and a common terminal 160. FIG. Multiplexer 100 is connected to antenna 2 at common terminal 160 . An inductor 3 for impedance matching is connected between the connection path between the common terminal 160 and the antenna 2 and the ground. Inductor 3 may be connected in series between common terminal 160 and antenna 2 . The inductor 3 may be included in the multiplexer 100 or may be externally attached to the multiplexer 100 . Also, the inductor 3 may be a capacitor or a composite circuit consisting of an inductor and a capacitor.

The filter 50 is an example of a first filter, and is applied to a transmission filter (transmission band: 824-849 MHz) of Band 26 of LTE (Long Term Evolution).

The acoustic wave filter 40 is applied to a reception filter (reception band: 859-894 MHz) of Band 26 of LTE.

The input/output terminal 140 of the filter 50 and the input/output terminal 110 of the acoustic wave filter 40 are connected to a common terminal 160, and the multiplexer 100 according to this embodiment is applied to a duplexer of Band 26 of LTE.

The filter 50 has an input/output terminal 140 (third input/output terminal) and an input/output terminal 150 (fourth input/output terminal), and is a ladder-type elastic wave filter composed of a plurality of elastic wave resonators. The filter 50 includes series arm resonators 51s, 52s, 53s and 54s and parallel arm resonators 51p, 52p and 53p. Series arm resonators 51 s, 52 s, 53 s and 54 s are arranged in series on a path connecting input/output terminal 140 and input/output terminal 150 . Parallel arm resonators 51p, 52p and 53p are connected between nodes on the path and the ground, respectively. With this configuration, the filter 50 constitutes a bandpass filter whose passband is the transmission band of the Band 26 of LTE.

Elastic wave filter 40 has the same circuit configuration as elastic wave filter 40 according to the embodiment, and uses Love waves as elastic waves. The five IDT electrodes 11 to 15 and reflectors 19A and 19B of the longitudinal coupling resonance section 10 and the five IDT electrodes 21 to 25 and reflectors 29A and 29B of the longitudinal coupling resonance section 20 are shown in FIG. , and the standard deviation SD of the pitch deviation rates D(k) of the longitudinally coupled resonators 10 and 20 is 2.92%.

8 is a graph comparing pass characteristics and isolation characteristics of multiplexers according to Example 1 and Comparative Example 1. FIG. FIG. 9 is a graph comparing the voltage standing wave ratios of the multiplexers according to Example 1 and Comparative Example 1. In FIG.

The circuit configuration of the multiplexer according to Comparative Example 1 is the same as the circuit configuration of the multiplexer 100 according to Example 1 shown in FIG. The difference is that the electrode finger pitches P(k) of the longitudinally coupled resonators constituting (the elastic wave filter 40) are regularly distributed. In other words, the standard deviation SD of the pitch deviation rate D(k) of the longitudinally coupled resonator constituting the reception filter according to Comparative Example 1 is less than 1.4%.

As shown in (a) of FIG. 8, there is no difference in the pass characteristics of the transmission filter (filter 50) between the first embodiment and the first comparative example. This is because the transmission filter according to Example 1 and the transmission filter according to Comparative Example 1 have the same circuit configuration and the same electrode finger configuration.

On the other hand, as shown in FIG. 8(b), with respect to the pass characteristics of the reception filter, Example 1 has better attenuation characteristics in the transmission band than Comparative Example 1 (enclosed by a dashed line in the figure). .

Further, as shown in FIG. 8(c), regarding the isolation characteristics between the transmission filter and the reception filter, the first embodiment is superior to the comparative example due to the improvement of the attenuation characteristics of the reception filter. 1, the isolation characteristics in the transmission band (enclosed by a dashed line in the figure) are improved.

Although not shown in FIG. 8, the pass characteristics of the reception filter and the transmission filter in the attenuation band on the lower frequency side than the transmission band of Band 26 and the attenuation band on the higher frequency side than the reception band of Band 26 There is no difference between Example 1 and Comparative Example 1 in terms of pass characteristics and isolation characteristics between the transmission filter and the reception filter (elastic wave filter 40).

Further, as shown in FIGS. 9A and 9C, the voltage standing wave ratios on the input side and the output side in the reception band of the reception filter according to Example 1 are smaller than those of Comparative Example 1. Therefore, the impedance characteristic of the reception filter is also improved.

The improvement of the attenuation characteristics of the reception filter according to the first embodiment, the improvement of the impedance characteristics, and the improvement of the isolation characteristics between the reception filter and the transmission filter are achieved by the electrode finger pitch P ( By setting k) as an irregular distribution and increasing the standard deviation SD of the pitch deviation rate D(k), it is possible to inhibit the excitation of unnecessary acoustic waves and suppress the propagation of unnecessary signals. be done.

FIG. 10 is a graph showing the relationship between the standard deviation SD of the pitch deviation rate D(k) of the longitudinally coupled resonator 1 and the isolation of the multiplexer 100. In FIG. The figure shows the correlation between the standard deviation SD of the pitch deviation rate D(k) of the longitudinally coupled resonator 1 of the elastic wave filter 40 and the isolation of the transmission band in the multiplexer 100 according to the first embodiment. ing. According to FIG. 10, by setting the standard deviation SD of the pitch deviation rate D(k) to 1.4% or more, the isolation improvement effect (1 dB or more) in the transmission band is obtained. Further, in the range of the standard deviation SD from 1.4% to 3.0%, the isolation of the transmission band improves as the standard deviation SD increases.

[4. Configuration and characteristics of elastic wave filter 40A according to embodiment 2]
FIG. 11A is a circuit configuration diagram of an elastic wave filter 40A according to the second embodiment. As shown in the figure, the elastic wave filter 40A includes a longitudinal coupling resonator 10A, series arm resonators 33s and 34s, parallel arm resonators 33p and 34p, and input/output terminals 110 and 120. FIG. The elastic wave filter 40A according to Example 2 differs from the elastic wave filter 40 according to the embodiment mainly in the configuration of the longitudinal coupling resonator 10A. In the following, the acoustic wave filter 40A according to the second embodiment will be described with a focus on the different configurations, omitting the same configurations as those of the acoustic wave filter 40 according to the embodiment.

Series arm resonators 33 s and 34 s are elastic wave resonators arranged in series on a path connecting input/output terminal 110 and input/output terminal 120 . Parallel arm resonators 33p and 34p are elastic wave resonators connected between nodes on the path and the ground, respectively.

The longitudinally coupled resonator 10A includes seven IDT electrodes arranged side by side in the elastic wave propagation direction on a substrate having piezoelectric properties, and arranged adjacent to the seven IDT electrodes in the elastic wave propagation direction. and two reflectors. Each of the seven IDT electrodes and the two reflectors constitutes a surface acoustic wave resonator together with a piezoelectric substrate. Each of the seven IDT electrodes and the two reflectors includes a plurality of electrode fingers Fe extending in a direction intersecting the acoustic wave propagation direction and arranged parallel to each other.

The elastic wave filter 40A uses low-speed Rayleigh waves as elastic waves, and constitutes a band-pass filter whose passband is the reception band (925 to 960 MHz) of Band 8 of LTE.

The seven IDT electrodes and two reflectors of the longitudinal coupling resonator 10A have an irregular electrode finger pitch P(k) distribution, and the pitch deviation rate D(k) of the longitudinal coupling resonator 10A is The standard deviation SD is 1.5%.

11B is a graph comparing the pass characteristics of the acoustic wave filters according to Example 2 and Comparative Example 2. FIG.

The circuit configuration of the elastic wave filter according to Comparative Example 2 is the same as the circuit configuration of the elastic wave filter 40A according to Example 2 shown in FIG. The difference is that the electrode finger pitch P(k) of the longitudinally coupled resonator 10A is regularly distributed. That is, the standard deviation SD of the pitch deviation rate D(k) of the longitudinally coupled resonator 10A configuring the acoustic wave filter according to Comparative Example 2 is less than 1.4%.

As shown in FIG. 11B , the elastic wave filter 40A according to the second embodiment has improved attenuation characteristics in the transmission band (880-915 MHz) and is in the passband more than the elastic wave filter according to the second comparative example. ripple is reduced.

According to this, by making the electrode finger pitch P(k) of the longitudinal coupling resonator 10A in the second embodiment irregularly distributed and increasing the standard deviation SD of the pitch deviation rate D(k), not only the attenuation band but also It is understood that ripples in the passband are reduced by inhibiting excitation of unnecessary acoustic waves generated in the passband.

[5. Configuration and characteristics of multiplexer according to embodiment 3]
The multiplexer according to the third embodiment has the same circuit configuration as the multiplexer 100 according to the first embodiment shown in FIG. The distribution mode of the electrode finger pitch P(k) of the resonator is different.

FIG. 12A is a graph showing the electrode finger arrangement and the electrode finger pitch distribution of the longitudinally coupled resonator 10 of the reception filter (elastic wave filter 40) according to the third embodiment. The lower part of FIG. 12A shows an electrode layout in which a part of the IDT electrode 11 forming the longitudinally coupled resonator 10 is enlarged. The IDT electrode 11 is composed of comb electrodes 11a and 11b. The comb-shaped electrode 11a is an example of a first comb-shaped electrode to which a signal potential (HOT) is applied, and the comb-shaped electrode 11b is an example of a second comb-shaped electrode connected to the ground. Electrode fingers Fe(1), Fe(3), Fe(5) and Fe(7) forming the comb-shaped electrode 11a, and electrode fingers Fe(2G), Fe(4G) and Fe(6G) forming the comb-shaped electrode 11b. ) are interleaved with each other.

The electrode finger pitches of adjacent electrode fingers Fe(1), Fe(3), Fe(5), Fe(7), . there is On the other hand, the electrode finger pitches of adjacent electrode fingers in the electrode fingers Fe(2G), Fe(4G), Fe(6G), . Note that the IDT electrode 11 has an irregular electrode finger pitch in the comb-shaped electrode 11a and a regularity in electrode finger pitch in the comb-shaped electrode 11b. , 1.4% or more.

That is, as shown in FIG. 12A, for example, under the condition that {P(2G)+P(3)} and {P(4G)+P(5)} are equal, P(1), P(2G) , P(3), P(4G), P(5), P(6G), P(7) . and

In the multiplexer according to the present embodiment, as shown in the upper part of FIG. 12A, the IDT electrodes 12 to 15 and the reflectors 19A and 19B of the longitudinally coupled resonator 10 constituting the reception filter (elastic wave filter 40) are The distribution of the electrode finger pitch P(k) is similar to that of the IDT electrode 11 described above.

12B is a graph comparing pass characteristics and isolation characteristics of multiplexers according to Example 3 and Comparative Example 3. FIG.

The circuit configuration of the multiplexer according to Comparative Example 3 is the same as the circuit configuration of the multiplexer according to Example 3, but compared with the multiplexer according to Example 3, the reception filter (acoustic wave filter 40) is configured. The difference is that the electrode finger pitch P(k) of the longitudinally coupled resonance portion is regularly distributed. In other words, the standard deviation SD of the pitch deviation rate D(k) of the longitudinally coupled resonator constituting the reception filter according to Comparative Example 3 is less than 1.4%.

As shown in (a) of FIG. 12B, there is no difference between the pass characteristics of the transmission filter (filter 50) between the third embodiment and the third comparative example. This is because the transmission filter according to Example 3 and the transmission filter according to Comparative Example 3 have the same circuit configuration and the same electrode finger configuration.

On the other hand, as shown in (b) of FIG. 12B , with respect to the pass characteristics of the reception filter, Example 3 has better attenuation characteristics (encircled with a dashed line in the figure) in the transmission band than Comparative Example 3. .

Further, as shown in (c) of FIG. 12B , regarding the isolation characteristics between the transmission filter and the reception filter, the third embodiment is superior to the comparative example due to the improvement of the attenuation characteristics of the reception filter. 3, the isolation characteristics in the transmission band (enclosed by a broken line in the figure) are improved.

The improvement of the attenuation characteristics of the reception filter and the improvement of the isolation characteristics between the reception filter and the transmission filter according to the third embodiment are achieved by the irregular distribution of the electrode finger pitch P(k) of the longitudinal coupling resonator in the third embodiment. By increasing the standard deviation SD of the pitch deviation rate D(k), it is possible to inhibit the excitation of unnecessary acoustic waves and suppress the propagation of unnecessary signals.

In addition, if the electrode finger pitch P(k) is not constant, manufacturing variations in the electrode finger pitch P(k) between the IDT electrodes will increase, and it is assumed that the transmission characteristics will deteriorate due to this. On the other hand, according to the above configuration, among the pair of comb-shaped electrodes constituting the IDT electrode 11, the electrode finger pitch P(k) of the grounded comb-shaped electrode 11b is constant, so that at least the comb-shaped electrode 11b , the electrode finger pitch P(k) can be manufactured with high accuracy. As a result, manufacturing variations in the electrode finger pitch P(k) between the IDT electrodes can be reduced, so deterioration of the pass characteristics can be suppressed.

In the multiplexer according to the present embodiment, the electrode finger pitch of the first comb-shaped electrode to which the signal potential (HOT) is applied is Due to the irregularity of P(k) and the regularity (equal pitch) of the electrode finger pitch P(k) in the second comb-shaped electrode connected to the ground, the pitch deviation rate D(k ) was set to 1.4% or more, but it is not limited to this. For example, as the arrangement configuration of the IDT electrodes of the longitudinally coupled resonator and the electrode fingers of the reflector, the irregularity of the electrode finger pitch P(k) in the second comb-shaped electrode connected to the ground and the signal potential (HOT) Due to the regularity (equal pitch) of the electrode finger pitch P(k) in the first comb-shaped electrode to which is applied, the standard deviation SD of the pitch deviation rate D(k) in the IDT electrode and reflector is set to 1.4% or more good too. This also reduces manufacturing variations in the electrode finger pitch P(k) between the IDT electrodes, thereby suppressing deterioration of the pass characteristics.

[6. Configuration and characteristics of multiplexer according to embodiment 4]
FIG. 13 is a configuration diagram of a multiplexer 200 and its peripheral circuits according to the fourth embodiment. As shown in the figure, the multiplexer 200 includes an acoustic wave filter 41, a filter 51, and a common terminal 160. Multiplexer 200 is connected to antenna 2 at common terminal 160 . An impedance matching circuit may be connected to the path connecting the common terminal 160 and the antenna 2 .

The filter 51 is applied, for example, to a reception filter for Band 26 of LTE. The filter structure of filter 51 is arbitrary.

The acoustic wave filter 41 is applied to, for example, a transmission filter for Band 26 of LTE.

The input/output terminal 140 of the filter 51 and the input/output terminal 110 of the acoustic wave filter 41 are connected to a common terminal 160, and the multiplexer 200 according to this embodiment is applied to a duplexer of Band 26 of LTE.

The elastic wave filter 41 has a filter circuit 43 and a longitudinally coupled resonator 42 .

The filter circuit 43 is provided on a piezoelectric substrate 60 . Filter circuit 43 is connected to input/output terminals 110 and 120, comprises one or more elastic wave resonators, and has a first frequency band as a passband. The first frequency band is, for example, the transmission band of Band 26 of LTE.

The longitudinally coupled resonator 42 is provided on the substrate 60, has IDT electrodes 42a and 42b arranged in parallel in the acoustic wave propagation direction, and has an input/output terminal 110, a node on a path connecting the input/output terminals 110 and 120, is connected to the filter circuit 43 and generates a signal having a reverse phase with respect to the signal component in a predetermined frequency band other than the first frequency band passing through the filter circuit 43 . The longitudinally coupled resonator 42 is a longitudinally coupled surface acoustic wave resonator including a surface acoustic wave resonator having an IDT electrode 42a and a surface acoustic wave resonator having an IDT electrode 42b. The longitudinally coupled resonator 42 has one end (IDT electrode 42 a ) connected to the input/output terminal 110 and the other end (IDT electrode 42 b ) connected to the series arm of the filter circuit 43 . One end and the other end of longitudinally coupled resonator 42 may be connected to a node on a series arm path connecting input/output terminals 110 and 120 of filter circuit 43 . Further, the longitudinally coupled resonator 42 may include reflectors arranged adjacent to the IDT electrodes 42a and 42b in the acoustic wave propagation direction. Also, the number of IDT electrodes that the longitudinally coupled resonator 42 has may be three or more . Also , the longitudinally coupled resonator 42 may be a surface acoustic wave filter, a transversal resonator, or a transversal filter, which consists of surface acoustic wave resonators having IDT electrodes.

With the above configuration, in the elastic wave filter 41, the signal component in the predetermined frequency band generated by the longitudinally coupled resonator 42 and the signal to be canceled among the signals transmitted through the filter circuit 43 (for example, the reception band of the LTE Band 26) When the signal components are summed, the amplitude of the summed signal can be made smaller than the amplitude of the original signal component to be canceled. More preferably, the cancellation signal component generated by the longitudinally coupled resonator 42 is a signal that is opposite in phase and has the same amplitude as the signal component to be canceled after passing through the filter circuit 43 .

Here, at least one of the IDT electrodes 42a, 42b and the reflector has a standard deviation SD of 1.4% or more of the pitch deviation rate D(k) in the above histogram.

According to this, when an acoustic wave corresponding to a predetermined frequency band of the longitudinally coupled resonator 42 propagates on the substrate 60, for example, the phase of the acoustic wave excited by the electrode finger Fe(k) and the electrode finger Fe(k+2 ) is likely to be out of phase with the acoustic wave excited by ), and mismatching in acoustic impedance is likely to occur. Therefore, it is possible to suppress the excitation of acoustic waves corresponding to the predetermined frequency band.

14 is a graph comparing pass characteristics of elastic wave filters according to Example 4, Comparative Example 4, and Comparative Example 5. FIG. The elastic wave filter 41 according to Example 4 has a standard deviation SD of 1.5% of the pitch deviation rate D(k). Further, the circuit configuration of the acoustic wave filter according to Comparative Example 4 is different from the acoustic wave filter 41 according to Example 4 in that the standard deviation SD of the pitch deviation rate D(k) is 1.1%. different. Further, the circuit configuration of the acoustic wave filter according to Comparative Example 5 differs from the acoustic wave filter 41 according to Example 4 only in that it does not have a longitudinally coupled resonator 42 .

In the pass characteristics of the elastic wave filters shown in FIG. 14 , the elastic wave filter 41 according to the fourth embodiment has a higher pass band (transmission band) than the elastic wave filters according to the comparative examples 4 and 5. The attenuation band (receiving band) located on the high frequency side has a large attenuation amount, and the band in which the attenuation band (receiving band) has a large attenuation amount is widened.

The reason why the attenuation in the attenuation band (reception band) of the elastic wave filter 41 according to the fourth embodiment is large is that the longitudinally coupled resonator 42 has an out-of-band excitation suppression effect due to the random pitch, and the attenuation band (reception band) is increased. It is understood that this is due to the fact that the ripple caused by the longitudinally coupled resonator 42, which reduces the amount of attenuation in the high frequency region in the band), is improved. Further, the reason why the attenuation band (receiving band) of the elastic wave filter 41 according to the fourth embodiment has a large attenuation amount is that the IDT electrode 42a and the IDT electrode 42b of the longitudinally coupled resonator 42 are widened due to the random pitch. It is understood that this is due to the optimization of the propagation characteristics between and.

Further, the improvement of the attenuation band (receiving band) of the elastic wave filter 41 makes it possible to provide the multiplexer 200 with improved isolation characteristics between the elastic wave filter 41 and the filter 51 .

[7. effects, etc.]
As described above, the elastic wave filter 40 according to the present embodiment includes the substrate 60 having piezoelectric properties, the plurality of IDT electrodes provided on the substrate 60 and arranged in parallel in the propagation direction of the elastic wave, and the plurality of IDT electrodes. and reflectors arranged adjacent to each other in the elastic wave propagation direction. , and a plurality of electrode fingers Fe arranged in parallel to each other. (2) three adjacent electrode fingers, namely, electrode finger Fe(k−1), electrode finger Fe(k), and electrode finger Fe(k+1), the electrode finger pitch P( k) and the interval average electrode finger pitch PM(k), which is the average of the electrode finger pitches P(k−1) and P(k+1), is the difference between the IDT electrode including the three adjacent electrode fingers or A value obtained by dividing the total average electrode finger pitch PT, which is the average pitch of all the electrode fingers of the reflector, is defined as the pitch deviation rate D(k) of the k-th electrode finger. The distribution of the pitch deviation rate D(k) obtained by calculating the pitch deviation rate D(k) for all the electrode fingers of the IDT electrode or reflector including the three adjacent electrode fingers is the pitch When defined as a histogram of deviation rates D(k), at least one of the plurality of IDT electrodes and reflectors has a standard deviation SD of pitch deviation rates D(k) in the histogram of 1.4% or more.

As a result, when an acoustic wave corresponding to a frequency band outside the pass band of the acoustic wave filter 40 propagates on the substrate 60, for example, the phase of the acoustic wave excited by the electrode finger Fe(k) and the phase of the electrode finger Fe(k+2) Therefore, the phase of the acoustic wave excited by is likely to be shifted, and mismatching of the acoustic impedance is likely to occur. Therefore, it is possible to suppress excitation of acoustic waves corresponding to frequency bands outside the pass band of the acoustic wave filter 40 . Further, when the acoustic wave excited by the electrode finger Fe(k) and the acoustic wave excited by the electrode finger Fe(k+2) on the input-side IDT electrode are picked up by the output-side IDT electrode, both acoustic waves are out of phase, they cannot be picked up efficiently. Therefore, it becomes possible to improve the attenuation characteristic of the acoustic wave filter 40 .

Further, each of the plurality of IDT electrodes is a first comb-shaped electrode including a portion of the electrode fingers Fe and a busbar electrode connecting one ends of the portion of the electrode fingers Fe. a second comb-shaped electrode including an electrode, another electrode finger among the plurality of electrode fingers, and a busbar electrode connecting the other ends of the other electrode fingers, and connected to the ground. . Here, the electrode fingers forming the first comb-shaped electrode and the electrode fingers forming the second comb-shaped electrode are interleaved with each other, and at least one of the plurality of IDT electrodes has a pitch deviation rate D The standard deviation SD of (k) may be 1.4% or more, and the electrode finger pitches of adjacent electrode fingers Fe in the electrode fingers Fe forming the second comb-shaped electrode may be equal over the second comb-shaped electrode.

If the electrode finger pitch P(k) is not constant, manufacturing variations in the electrode finger pitch between the IDT electrodes will increase, and it is assumed that the transmission characteristics will deteriorate in particular. In contrast, according to the above configuration, of the first comb-shaped electrodes and the second comb-shaped electrodes constituting the IDT electrodes, the electrode finger pitch P(k) of the second comb-shaped electrode connected to the ground is constant. , the electrode finger pitch P(k) of the second comb-shaped electrode can be manufactured with high accuracy, so that the deterioration of the transmission characteristic can be suppressed.

Further, at least one of the plurality of IDT electrodes has a standard deviation SD of 1.4% or more of the pitch deviation rate D(k) in the histogram, and adjacent electrode fingers among the electrode fingers constituting the first comb-shaped electrode may be equal across the first comb electrodes.

According to the above configuration, the electrode finger pitch P(k) of the first comb-shaped electrode to which the signal potential (HOT) is applied is constant among the first comb-shaped electrode and the second comb-shaped electrode that constitute the IDT electrode. Since the electrode finger pitch P(k) of the first comb-shaped electrode can be manufactured with high precision, it is possible to suppress the deterioration of the transmission characteristics.

Further, at least one of the plurality of IDT electrodes has a standard deviation SD of the pitch deviation rate D(k) in the histogram of 1.4% or more, and the reflector has a pitch deviation rate D(k) in the histogram of The standard deviation SD may be less than 1.4%.

As a result, manufacturing variations in the electrode finger pitch P(k) of the reflector can be suppressed, so that the attenuation pole outside the passband defined by the resonance operation of the reflector can be stabilized.

Further, one IDT electrode among the plurality of IDT electrodes has a standard deviation SD of 1.4% or more of the pitch deviation rate D (k) in the histogram, and the other IDT electrode among the plurality of IDT electrodes may have a standard deviation of less than 1.4% of the pitch deviation rate D(k) in the histogram.

As a result, only the IDT electrodes that greatly affect the attenuation characteristics have irregular pitches to improve the attenuation characteristics, and the other IDT electrodes have regular pitches to suppress characteristic deterioration due to manufacturing variations.

Further, each of the plurality of IDT electrodes has a standard deviation SD of the pitch deviation rate D (k) in the histogram of less than 1.4%, and the reflector has a standard deviation of the pitch deviation rate D (k) in the histogram may be 1.4% or more.

As a result, manufacturing variations in the electrode finger pitch of the IDT electrodes can be suppressed, so that the insertion loss in the passband can be stabilized.

The elastic wave filter 41 is provided on the substrate 60 having piezoelectric properties, is connected to the input/output terminals 110 and 120, is composed of elastic wave resonators, and is a filter circuit having a first frequency band as a passband. 43, and a plurality of IDT electrodes 42a and 42b provided on a substrate 60 and arranged side by side in the elastic wave propagation direction, and connecting the input/output terminal 110 and the input/output terminal 120 to each other. a longitudinally coupled resonator 42 connected to at least one of the paths connecting the IDT electrodes and generating a signal having a different phase with respect to a signal component in a predetermined frequency band other than the first frequency band passing through the filter circuit 43; 42a and 42b extend in a direction intersecting the elastic wave propagation direction and are composed of a plurality of electrode fingers arranged parallel to each other. The standard deviation of D(k) may be 1.4% or more.

According to this, it is possible to increase the amount of attenuation in a predetermined attenuation band in the filter circuit 43, and to widen the band in which the amount of attenuation in the attenuation band increases.

Further, multiplexer 100 according to the present embodiment has common terminal 160, elastic wave filter 40 having input/output terminals 110 and 120, input/output terminals 140 and 150, and has a pass band different from that of elastic wave filter 40. A common terminal 160 is connected to the input/output terminals 110 and 140 .

Thereby, the multiplexer 100 with improved isolation characteristics between the elastic wave filter 40 and the filter 50 can be provided.

(Other variations, etc.)
Although the elastic wave filter and multiplexer according to the present invention have been described above with reference to the embodiments and examples, the elastic wave filter and multiplexer of the present invention are not limited to the above-described embodiments and examples. . Other embodiments realized by combining arbitrary components in the above-described embodiments and examples, and various modifications of the above-described embodiments and examples that a person skilled in the art can think of without departing from the scope of the present invention. The present invention also includes modifications obtained by applying and various devices incorporating the acoustic wave filters and multiplexers in the above-described embodiments and examples.

For example, in the above embodiments and examples, a duplexer applied to Band 26 of LTE was exemplified as a multiplexer, and a reception filter applied to Band 8 of LTE was exemplified as an elastic wave filter. It is also applied to communication bands other than Band 8 and Band 26 of LTE. The multiplexer can be applied not only to a duplexer, but also to a triplexer in which three filters are commonly connected to an antenna, a hexaplexer in which three duplexers are commonly connected via a common terminal, and the like. That is, the multiplexer just needs to have two or more filters.

Further, the multiplexer according to the present invention is not limited to a configuration including both transmission filters and reception filters, and may be configured to include only a plurality of transmission filters or only a plurality of reception filters.

Further, in the elastic wave filters and multiplexers in the above embodiments and examples, another circuit element and wiring are inserted between the paths connecting the circuit elements (and parts) and signal paths disclosed in the drawings. may be

INDUSTRIAL APPLICABILITY The present invention can be widely used as a transmission/reception filter and multiplexer used in the front end of wireless communication terminals that require low loss in the passband and high attenuation outside the passband.

1 longitudinally coupled resonator 2 antenna 3 inductor 10, 10A, 20 longitudinally coupled resonator 11, 12, 13, 14, 15, 21, 22, 23, 24, 25, 42a, 42b IDT electrode 11a, 11b, 12a, 12b , 13a, 13b, 14a, 14b, 15a, 15b, 21a, 21b, 22a, 22b, 23a, 23b, 24a, 24b, 25a, 25b Comb electrodes 19A, 19B, 29A, 29B Reflectors 31s, 32s, 33s, 34s , 51s, 52s, 53s, 54s Series arm resonators 31p, 32p, 33p, 34p, 51p, 52p, 53p Parallel arm resonators 40, 40A, 41 Acoustic wave filter 42 Longitudinal coupling resonator 43 Filter circuit 50, 51 Filter 60 Substrate 100, 200 Multiplexer 110, 120, 140, 150 Input/output terminal 130 Terminal 160 Common terminal D Pitch deviation rate Fe Electrode finger P Electrode finger pitch PM Section average electrode finger pitch PT Whole average electrode finger pitch SD Standard deviation

Claims (8)

a piezoelectric substrate; a plurality of IDT (InterDigital Transducer) electrodes provided on the substrate and arranged in parallel in an elastic wave propagation direction; and arranged adjacent to the plurality of IDT electrodes in the elastic wave propagation direction. An acoustic wave filter comprising a longitudinally coupled resonator having a reflector and a
Each of the plurality of IDT electrodes and the reflector is configured by a plurality of electrode fingers arranged parallel to each other and extending in a direction intersecting the elastic wave propagation direction,
(1) defining the distance between the k-th (k is an integer equal to or greater than 2) electrode finger and the (k+1)-th electrode finger in the elastic wave propagation direction as the k-th electrode finger pitch,
(2) In three adjacent electrode fingers of the (k−1)-th electrode finger, the k-th electrode finger, and the (k+1)-th electrode finger, the k-th electrode finger pitch and (k−1) The difference between the interval average electrode finger pitch, which is the average of the th electrode finger pitch and the (k+1) th electrode finger pitch, is the total number of electrode fingers of the IDT electrode or reflector including the three adjacent electrode fingers. A value obtained by dividing the average pitch by the overall average electrode finger pitch is defined as the pitch deviation rate of the k-th electrode finger,
(3) Distribution of the pitch deviation rate obtained by calculating the pitch deviation rate of the k-th electrode finger for all the electrode fingers of the IDT electrode or reflector including the three adjacent electrode fingers. is defined as the histogram of the pitch deviation rate,
At least one of the plurality of IDT electrodes and the reflector has a standard deviation of the pitch deviation rate in the histogram of 1.4% or more.
Acoustic wave filter. Each of the plurality of IDT electrodes,
a first comb-shaped electrode including some of the plurality of electrode fingers and a busbar electrode connecting one ends of the some of the electrode fingers;
a second comb-shaped electrode connected to the ground, which is composed of the other electrode fingers of the plurality of electrode fingers and a busbar electrode connecting the other ends of the other electrode fingers to each other; ,
the electrode fingers forming the first comb-shaped electrode and the electrode fingers forming the second comb-shaped electrode are inserted into each other,
At least one of the plurality of IDT electrodes has a standard deviation of the pitch deviation rate in the histogram of 1.4% or more, and adjacent electrode fingers constituting the second comb-shaped electrode of the at least one IDT electrode the electrode finger pitch of the electrode fingers is equal across the second comb-shaped electrode;
The elastic wave filter according to claim 1. Each of the plurality of IDT electrodes,
a first comb-shaped electrode including some of the plurality of electrode fingers and a busbar electrode connecting one ends of the some of the electrode fingers;
a second comb-shaped electrode connected to the ground, which is composed of the other electrode fingers of the plurality of electrode fingers and a busbar electrode connecting the other ends of the other electrode fingers to each other; ,
the electrode fingers forming the first comb-shaped electrode and the electrode fingers forming the second comb-shaped electrode are inserted into each other,
At least one of the plurality of IDT electrodes has a standard deviation of the pitch deviation rate in the histogram of 1.4% or more, and adjacent electrode fingers constituting the first comb-shaped electrode of the at least one IDT electrode the electrode finger pitch of the electrode fingers is equal across the first comb-shaped electrode;
The elastic wave filter according to claim 1. At least one of the plurality of IDT electrodes has a standard deviation of the pitch deviation rate in the histogram of 1.4% or more,
The reflector has a standard deviation of the pitch deviation rate in the histogram of less than 1.4%.
The elastic wave filter according to any one of claims 1 to 3. One IDT electrode among the plurality of IDT electrodes has a standard deviation of the pitch deviation rate in the histogram of 1.4% or more,
Other IDT electrodes among the plurality of IDT electrodes have a standard deviation of the pitch deviation rate in the histogram of less than 1.4%.
The elastic wave filter according to any one of claims 1 to 4. Each of the plurality of IDT electrodes has a standard deviation of the pitch deviation rate in the histogram of less than 1.4%,
The reflector has a standard deviation of the pitch deviation rate in the histogram of 1.4% or more,
The elastic wave filter according to claim 1. a piezoelectric substrate;
a filter circuit provided on the substrate, connected to the first input/output terminal and the second input/output terminal, comprising an elastic wave resonator, and having a first frequency band as a pass band;
a plurality of IDT electrodes provided on the substrate and arranged side by side in an elastic wave propagation direction, the first input/output terminal, the second input/output terminal, and the first input/output terminal and the second input/output terminal; and a longitudinally coupled resonator that is connected to at least one of the paths connecting to and generates a signal having a different phase with respect to a signal component in a predetermined frequency band other than the first frequency band passing through the filter circuit. ,
The plurality of IDT electrodes extend in a direction intersecting the elastic wave propagation direction and are composed of a plurality of electrode fingers arranged parallel to each other,
(1) defining the distance between the k-th (k is an integer equal to or greater than 2) electrode finger and the (k+1)-th electrode finger in the elastic wave propagation direction as the k-th electrode finger pitch,
(2) In three adjacent electrode fingers of the (k−1)-th electrode finger, the k-th electrode finger, and the (k+1)-th electrode finger, the k-th electrode finger pitch and (k−1) The difference between the interval average electrode finger pitch, which is the average of the th electrode finger pitch and the (k+1) th electrode finger pitch, is the average pitch of the entire electrode fingers of the IDT electrode including the three adjacent electrode fingers. A value obtained by dividing by a certain overall average electrode finger pitch is defined as the pitch deviation rate of the k-th electrode finger,
(3) The distribution of the pitch deviation rate obtained by calculating the pitch deviation rate of the k-th electrode finger for all the electrode fingers of the IDT electrodes including the three adjacent electrode fingers is If defined as a histogram of the pitch deviation rate,
At least one of the plurality of IDT electrodes has a standard deviation of the pitch deviation rate in the histogram of 1.4% or more.
Acoustic wave filter. a common terminal;
The acoustic wave filter according to any one of claims 1 to 7, which has a first input/output terminal and a second input/output terminal;
A first filter having a third input/output terminal and a fourth input/output terminal and having a different pass band from the elastic wave filter,
The common terminal is connected to the first input/output terminal and the third input/output terminal,
multiplexer.

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